Final answer:
China became involved in the Korean War to support North Korea, assert authority, and protect its interests.
Step-by-step explanation:
China became involved in the Korean War for several reasons. Firstly, Mao Zedong, the leader of China at the time, favored sending aid to North Korea and supporting fellow communist nations. Secondly, China saw an opportunity to assert its authority and regain control of the Korean Peninsula. Thirdly, China was concerned about the presence of the United States near its borders and wanted to protect its interests.